Original paper

Der Grenzbereich Silur-Devon im Südwest-Harz

Maronde, Hans-Dietrich

Abstract

A number of new localities yielding graptolites could be found in the course of stratigraphic and tectonic investigations in the Upper Silurian and Lower Devonian of the southwestern part of the Harz mountains (sheet: Bad Lauterberg No. 4328 and sheet: Zorge No. 4329, scale 1:25 000). The existence of the upper eß1 near Bad Lauterberg and of the Scyphocrinus-horizon (transgrediens-zone, eß2) near Wieda is emphasized. Here the base of the Lower Devonian is represented by slates with a fauna of the uniformis-zone which is the first proof of sediments of Lower Gedinnian age in the Harz mountains. Contrary to other authors the only 0,5 m thick limestone-lens of the Wieda-brook Starts in the Budnanian extending to the Pragian. A nearly continuous, marine Sedimentation exists in the Wieda region at the Silurian-Devonian boundary while in the Bad Lauterberg area there is a stratigraphic gap of unknown origin. The base of the Devonian is defined by the appearence of Monograptus uniformis PRIBYL according to common international use. Results especially in the area NW of Bad Lauterberg indicate that the isoclinal folds are overturned to the NW and are associated with imbricate structures. Great differences in the mobility of the sedimentary units are responsible for the disharmonic folding and the imbricate structures both resulting from the Variscan orogeny. There is no evidence of orogenic activity at the Silurian-Devonian boundary corresponding to the late Caledonian folding.